1. Field of the Invention
This invention relates generally to gas lasers, and more particularly, to an improved high power, large double bore RF powered gas laser.
2. Description of the Related Art
It is generally known that higher power output energy can be obtained from a gas laser if the diameter of the laser chamber is made larger. For example, a waveguide laser will have a laser chamber which is about 1-2 millimeters in cross-section, while a higher power, large bore laser will have a laser chamber which ranges from about 0.25 inches in diameter to over 0.5 inches in diameter. Furthermore, the length of the laser chamber in such large bore, higher power lasers is also increased. Such elongated laser chambers usually have continuous, smooth internal side walls which reflect unwanted low angle laser light energy traveling along the length of the laser chamber, at a slight angle to the length of the laser chamber. At this slight angle, the reflections work their way around the inside diameter of the laser chamber, and produce unwanted laser modes which are difficult to deal with. One known way to reduce these laser wall modes is by placing apertures inside the laser chamber. However, these internal apertures reduce laser output power. Apertures may also be placed outside of the laser chamber for clipping the unwanted laser energy.
U.S. Pat. No. 4,589,114, discloses a gas laser having an elongated cylindrical chamber with a plurality of groves formed on the internal surface to provide optical mode control. Additionally, this patent discloses numerous electrode configurations to transversely excite the gas, such as CO.sub.2, in the cylindrical chamber, to produce a laser discharge which is reflected and guided by a pair of reflectors mounted at the ends of the cylindrical chamber. This patent, however, fails to disclose a double bore laser.
U.S. Pat. Nos. 4,596,018 and 4,618,916 also disclose gas discharge lasers having elongated cylindrical laser chambers with external electrodes transverse to the laser chamber. These patents, however, also fail to disclose double bore lasers.
Another problem seen with an increase in gas laser size is that acoustic waves are generated within the gas laser discharge thus affecting the rate at which the laser can be modulated. Most lasers do not operate in the continuous wave mode but are modulated at a frequency between 0 and 60 KHz. Therefore, when the laser modulation rate and the acoustic waves inside the laser are at the same frequency, the laser output power is reduced dramatically.
There is, therefore, a need in the art for an improved RF powered high power laser. The present invention provides such an improvement, by reducing unwanted wall reflections without losing laser output power, and reducing acoustic waves inside the laser cavity to a level which does not affect the power output during modulation.